Percussion electrical hand-held tool

ABSTRACT

The present invention relates to a percussion electrical hand-held tool having an electronic control unit ( 5 ) for controlling at least one power parameter of the electrical tool, and a substantially flat force sensor for controlling operation of the electronic control unit ( 5 ) and arranged sliding displacement-free for sensing a press-on force (F, F 1 ) applied by a user in an operational direction of the electric tool, without being displaced, between at least two, associated with each other, press-surfaces ( 7   a   , 7   b ) extending at least partially transverse to a percussion axis (A) of the electrical tool.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a percussion electricalhand-held tool such as trepan or a chisel power tool for working stonematerials.

[0003] 2. Description of the Prior Art

[0004] In the electrical hand-held tools of the type described above, anaxial impact energy, which is generated by a percussion mechanism istransmitted to percussion working tool for working a workpiece. Aportion of the energy, through the handle, acts on a tool user, causingdisturbing vibrations in the user hand.

[0005] A large press-on force, which is applied to the handle, isassociated, in percussion hand-held tools, with an intuitive desire toincrease the break-down output. Contrary to that, in pure rotary tools,an increase press-on force leads to reduction of the rotational speed.Power parameters of a break-down work include, in particular, impactpower, impact frequency, and optionally, rotational speed of thepercussion power tool.

[0006] German Publication DE-19649468 discloses an electrical hand-heldtool with control means being provided in the guide handle or in theauxiliary handle.

[0007] German Publication DE-3843960 discloses controlling an operationof control electronic of an electrical hand-held tool by a functionalpotentiometer with a pressure pad.

[0008] German Publication DE-19510365 discloses the use, in a functionalpotentionmeter, of a compressible medium in form of a fluid that isprovided in the control member between a pressure plate and a sensor fortransmitting pressure.

[0009] U.S. Pat. No. 4,250,434 discloses the use of an electropheumaticsensor, which is formed as a flexible pressure hose, for controlling amachine.

[0010] German Publication DE-19703746 discloses an arrangement of adamping element on the rear gripping surface of a handle of anelectrical hand-held tool.

[0011] U.S. Pat. No. 5,987,705 discloses a handle with a pressure sensorwhich controls a pump for generating a vibration suppressing fillingpressure.

[0012] German Publication DE-3316013 discloses a hammer drill with acontrol member or servo component arranged on the tool housing forsteplessly controlling an impact energy of the hammer drill.

[0013] In German Publication DE-4231986, a mechanical control of thecoupling of the percussion mechanism of a hammer drill is effected byusing a press-on force applied by the power tool to a workpiece.However, the necessary, movable relative to each other and slidable oneach other, parts cannot be used in the rough environment of theconstructional industry, as the penetrating dust reduces the operationalreliability of such electrical tool.

[0014] An object of the present invention is to provide a slidingmovement-free, intuitive control of a power parameter, in particular, ofan axial impact energy of a percussion electrical hand-held tool.

[0015] Another object of the present invention is to preventtransmission of vibration to a tool user hand.

SUMMARY OF THE INVENTION

[0016] These and other objects of the present invention, which willbecome apparent hereinafter, are achieved by providing a percussionelectrical hand-held tool including an electronic control unit forcontrolling at least one power parameter of the electrical tool, and asubstantially flat force sensor for controlling operation of theelectronic control unit and arranged, free of sliding displacement, forsensing a press-on force applied by a user in an operational directionof the electric tool between at least two, associated with each other,press services extending at least partially transverse to a percussionaxis of the electrical tool.

[0017] The arrangement of a flat force sensor, according to the presentinvention, between associated press-surfaces for a displacement-freesensing of a press-on force for controlling a power parameter, can besafely used even in a rough environment.

[0018] Advantageously, the force sensor is formed as an, eletropheumaticsensor with a hollow pheumatic force transmission member located betweena pressure surface and a force sensing element.

[0019] Advantageously, the force transmission member is filled with aneasily deformable, pressure transmitting medium or a fluid, pressuretransmitting medium, e.g., pneumo-oil, gel, or high viscouls solidnon-free flowing, non-evaporative material.

[0020] Advantageously, the hollow pneumatic force transmission member isformed as a cushion or hose the cross-section of which becomescompressed upon application of press-on force, and becomes deformed,which increases the hydrostatic pressure of the pressure transmittingmedium.

[0021] Advantageously, the force sensor is located in a front section ofthe tool, behind an axial position of the tool chuck or behind thespindle bearing, which permits to measure the entire press-on force.

[0022] Advantageously, the force transmission member extends up to thehandle, which makes possible to measure the entire press-on force actingon the force sensing element in the handle.

[0023] Advantageously, the press-surfaces are arranged, with respect toa force flux, between the percussion mechanism and a gripping surface ofthe handle.

[0024] More advantageously, the press-surfaces are arranged in a regionof working tool-side, axial position of the percussion mechanismrelative to a tool outer casing of which the handle forms a part, or ina region of a modular position of a drive module and a handle module.

[0025] Advantageously, the force transmission member extends transverseto the percussion axis and is arranged between the handle and avibration-proof grripping casing, whereby the vibration in the pressuretransmission medium are damped and are prevented from being transmittedto the user hand.

[0026] Advantageously, the tool side handle is also provided with aforce-sensor forming, force transmission member provided with a forcesensing element electrically connected, via signal conductors, with theforce sensing element in the handle, whereby the sum of press-on forcesof both the handle and the side handle are used for control purposes.

[0027] Alternatively, the force transmission member of the side handlecan be connected directly with the force transmission element in thehandle, which permits to use a common force sensing element, without theuse, in the front portion of the power tool, current conductingconductors, which eliminates the safety problems associated with suchconductors.

[0028] Advantageously, there is provided a low-pass filter with acut-off voltage of less than 30 Hz between the control unit and theforce sensor. The low-pass filter filters out the low frequency controlsignals and suppress the high frequency vibrations.

[0029] The novel features of the present invention, which are consideredas characteristic for the invention, are set forth in the appendedclaims. The invention itself, however, both as to its construction andits mode of operation, together with additional advantages and objectsthereof, will be best understood from the following detailed descriptionof preferred embodiment, when read with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings show:

[0031]FIG. 1 a side, partially cross-sectional view of an electricalhand-held tool according to the present invention; and

[0032]FIG. 2 a perspective view of a force sensor used in the inventiveelectrical hand held tool.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] An axially percussion, electrical hand-held tool 1 according tothe present invention, which is shown in FIG. 1, includes a percussionmechanism 2, an electrical motor 3 for driving the percussion mechanism2, a handle 4, and a electronic control unit 5 formed as a phase-firedcontrol unit. The phase-fired control unit 5 is itself controlled by asubstantially flat force sensor 6 which is arranged transverse to thepercussion axis a press-on force F applied by a user to the handle 4 inan operational direction of the electrical tool. The force sensor isarranged, free of any sliding movement, between two, associated witheach other press-surfaces 7 a, 7 b provided between the percussionmechanism 2 and a gripping surface 8 of the handle 4.

[0034] In FIG. 1, three different arrangements of press-surfaces 7 a, 7b are schematically shown. According to the first arrangement I, thepress-surfaces 7 a, 7 b are arranged with respect to the force sensor6″, at the working tool-side position of the percussion mechanism 2 withrespect to the outer casing 9. According to the second arrangement II,the press-surfaces 7 a, 7 b are arranged, with respect to the forcesensor 6″ in the modular position of the drive module 10 with respect tothe handle module 11. According to the third arrangement III, thepress-surfaces 7 a, 7 b are arranged, with respect to the force sensor6, between the handle 4 and a gripping casing 12 that is protected, tosome extent, from vibrations by the flat sensor 6. A force sensor 6′″ ina side handle is directly pneumatically connected with the handle 4 by aconnection hose 14. The circular sensor 6″ is arranged in the frontsection of the electrical tool 1 in the region of the axial position ofa chuck 20, adjacent to a ball bearing 21, and is connected with thehandle 4 by an extension of the connection hose 14 or is connected withthe sensor 6. A low-pass filter 19 is arranged between the output of thesensor 6 and the phase-controlling unit 5 (FIG. 1).

[0035] According to the embodiment of a force sensor, shown in FIG. 2,the force sensor 6 is formed as an electropneumatic sensor provided witha force transmission member 17 between a pressure surface 15 and a forcesensing element 16. The force transmission member 17 is filled withpressure transmitting medium 18 and is formed as a rather flat closedhose.

[0036] Though the present invention was shown and described withreferences to the preferred embodiment, such is merely illustrative ofthe present invention and are not to be construed as a limitationthereof and various modifications of the present invention will beapparent to those skilled in the art. It is therefore not intended thatthe present invention be limited to the disclosed embodiment or detailsthereof, and the present invention includes all variations and/oralternative embodiments within the spirit and scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. A percussion electrical hand-held tool,comprising a percussion mechanism (2); a handle (4); electronic controlmeans (5) for controlling at least one power parameter of the electricaltool; and a substantially flat force sensor (6) for controllingoperation of the electronic control means (5) and arranged, for sensinga press-on force (F, F¹) applied by a user in an operational directionof the electrical tool, free of sliding displacement, between at leasttwo, associated with each other, press-surfaces (7 a, 7 b) extended atleast partially transverse to a percussion axis (A) of the electricaltool.
 2. An electrical hand-held tool according to claim 1, wherein theforce sensor (6) is formed as an electropneumatic sensor comprising ahollow pneumatic force transmission member (17) located between apressure surface (15) and a force sensing element (16).
 3. An electricalhand-held tool according to claim 2, wherein the force transmissionmember (17) is filled with one of an easily deformable pressuretransmitting medium and a fluid pressure transmitting medium.
 4. Anelectrical hand-held tool according to claim 1, further comprising anadditional side handle (13) including a force transmission means forforming a further substantially flat force sensor (6′″).
 5. Anelectrical hand-held tool according to claim 2, wherein the forcetransmission member (17) is formed as one of a cushion and a hose.
 6. Anelectrical hand-held tool according to claim 1, wherein the force sensor(6″) is located in a front section of the tool behind an axial positionof an electrical tool chuck (20).
 7. An electrical hand-held toolaccording to claim 2, wherein the force transmission member extends upto the handle (4).
 8. An electrical hand-held tool according to claim 1,wherein the press-surfaces (7 a, 7 b) are arranged, with respect to aforce flux, between the percussion mechanism (2) and a gripping surfaceof the handle (4).
 9. An electrical hand-held tool according to claim 8,wherein the press-surfaces (7 a, 7 b) are arranged in a region of aworking tool-side axial position of the percussion mechanism (2)relative to a tool outer casing (9) of which the handle (4) forms apart.
 10. An electrical hand-held tool according to claim 8, wherein thepress-surfaces (7 a, 7 b) are arranged in a region of a modular positionof a drive module (10) and a handle module (11) of which the handle (4)forms a part.
 11. An electrical hand-held tool according to claim 1,wherein the press-surfaces (7 a, 7 b) are arranged between the handle(4) and a vibration-proof gripping casing (12).
 12. An electricalhand-held tool according to claim 1, further comprising a side handle(13) containing a force-transmission member, and a connection hose (14)that pneumatically connects the force transmission member of the sidehandle (13) with a force transmission member provided in the handle (4).13. An electrical hand-held tool according to claim 1, furthercomprising a low-pass filter (19) having a cut-off frequency of lessthan 30 H_(z) for connecting the force sensor (6) with the electroniccontrol means.